In the race to find the weirdest planet orbiting another star, we may have a front runner: GJ 667Cc, a super-Earth orbiting one star in a triple system that’s actually relatively closeby. And oh yeah: it just so happens to be in just the right spot to be potentially inhabitable!

Of course, I have some caveats, so don’t get too excited. But this is a weird and pretty cool one!

GJ 667 is a triple star system that’s right in our back yard as these things go: it’s only about 22 light years away, making it one of the closest star systems in the sky. It’s composed of two stars a bit smaller and cooler than the Sun which orbit each other closely, and a third, smaller star orbiting the pair about 35 billion km (20 billion miles) out. Stars in multiple systems get capital letters to distinguish them, so the two in the binary are GJ 667 A and B, and the third one is GJ 667C.

That third star is the interesting one. It’s a cool, red M dwarf with about a third the diameter of the Sun. Fainter, too: it only puts out about 1% of the light the Sun does. It’s been studied for years to look for planets around it, and while there have been some signs found, this new research is the first solid detection of planets that’s been published.

They used the Doppler method (sometimes called the Reflexive Velocity method): as planets orbit a star, their gravity tugs on it. We usually can’t see this motion directly, but a spectrum can reveal a Doppler shift, similar to the change in pitch you hear when a car or train goes by. If the spectrum has a high enough resolution, and the analysis very carefully done, there’s a lot you can tell by measuring it. You can get the planet’s mass, its period, and even the shape of its orbit.

In this case, the spectrum reveals GJ 667C may have four planets! Two very strong signals pop up with periods of 7 and 28 days, a third one at 75 days, and a possible trending shift in the spectrum that may point to a planet orbiting in a very roughly 20 year period.

It’s that second planet, GJ 667C with a 28 day orbit that’s so interesting. Its mass is at least 4.5 times that of the Earth, so it’s hefty. A 28 day orbit puts it pretty close to the parent star — about 7 million kilometers, or less than 5 million miles (Mercury is 57 million km from the Sun, by comparison). But remember, GJ 667C is a very dim bulb, so being that close means that the planet is actually right in the middle of the star’s habitable zone! The HZ is the distance where liquid water could exist on a planet — it depends on the size and temperature of a star, and also on the planet’s characteristics. A cloudy planet can hold heat better through the greenhouse effect, so it can be farther from the star and still be warm, for example.
So this planet, if it’s rocky, might have liquid water! Of course, we know nothing about the planet itself except its mass, and even that’s a lower limit, due to the physics of how it’s measured based on the star’s spectrum. Still, we can use that number and play a bit. You might think that mass gives it a crushingly higher gravity than Earth. But wait!

The gravity you feel standing on the surface of a planet does depend on its mass — double the mass and you double the gravity — but it also depends on the inverse square of its size. So if you keep it the same mass but double the radius, the gravity drops by a factor of 4. So if GJ 667Cc has 4.5 times the Earth’s mass, but is twice as big, the gravity on the surface could be quite close to ours.

My point: don’t judge a planet by its mass until you know its girth.

Of course, we don’t know if this planet has an atmosphere or anything like that, either. It seems likely; it should have enough gravity to hold onto some gases. And if it does have an atmosphere, we don’t know if it has water or anything like that.

So there are a lot of unknowns here (which is why I warned you not to get too excited up front), but even so, there’s some reason to be hopeful. Why?

Two reasons. One is that these dinky red dwarf stars are by far the most numerous in the galaxy. They outnumber stars like the Sun by nearly 10 to 1. So if this one has a planet — and in a triple system! — then it’s likely that planets are extremely common in the galaxy. We’re getting that from lots of different studies, but it’s nice to see that fall into line here, too.

Second, remember, it’s close by (not that we’ll be heading there any time soon, but still). 20 light years is nothing compared to he 100,000 light year diameter of our galaxy. Just by random chance, having a planet even remotely Earthlike at that distance implies there are billions more in our galaxy alone!

Third, these stars are deficient in heavy elements. The spectrum of GJ 667C reveals it has far less things like oxygen and iron in it than the Sun does. Studies have shown that stars like this are less likely to have planets than stars like the Sun, which are rich in there elements. Maybe we got lucky that a nearby deficient star has planets, or maybe the earlier work is off a bit and stars like this do have planets. Either way, it again implies planets are extremely abundant in the galaxy.

So no matter how you look at it, this is good news. And it’s one step closer to the big goal of exoplanet astronomy: finding another Earth. That day is approaching. Maybe even soon.

Image credits: G. Anglada-Escudé using the program Celestia; G. Anglada-Escudé/DSS.

Perhaps instead of a potentially habitable planet this group has instead found an alias of the moon?

These ground-based observations are often dictated by lunar phases, and a 28 day planet is awfully close to a lunar cycle. Have a look at the coverage of the planet candidate in their phase-folded RV curve, the top-right panel of Fig. 2. The high density of points near phase 0 and the paucity of points near +/-14 days should have set the threshold for detection much higher than 0.034% — this is not yet a 4 sigma detection. Given that the authors had to also first subtract a long-term trend with a best-fit period of 7100 +/- 3000 days, who knows what sort of additional aliases they have introduced into the data.

I find news like these breathtaking. Not just this one in particular but the fact that I’m starting to gradually read more and more about exoplanets that are similar to our own.

Just a question. You wrote: “It’s that second planet, GJ 667C with a 28 day orbit that’s so interesting.”
I thought GJ 667C was the star, not the planet. Shouldn’t that planet be named something like “GJ 667C b”?

I’m just amazed at the dynamics of this n-body problem as well. Even though C is pretty far from the other two stars, there has to be a lot of strange effects going on there. And even still there are planets.

Your second point:

Second, remember, it’s close by (not that we’ll be heading there any time soon, but still). 20 light years is nothing compared to the 100,000 light year diameter of our galaxy. Just by random chance, having a planet even remotely Earthlike at that distance implies there are billions more in our galaxy alone!

While it is indeed a datapoint, we still suffer from a lack of datapoints. It could just be coincidence that there are two systems within 22 lightyears that have earthlike worlds around them. We need to find a few more before definitively state that implication (not that I actually disagree with you, I just think it may be a bit premature at this point to come to that conclusion). All in all, still incredibly cool, and weird, news. 😀

This one is massive, so it’s not entirely certain it is rocky – it could end up having a very low density, being a “puffy planet” with no surface. But this is far more likely to be a rocky planet than, say, Kepler-22b: I see both this one and Gliese 581 d as probably being similar worlds (100 km-deep world-oceans anyone?? :))

But either way: I ARE EXCITE!! 😀 And in a trinary system too – how’s that for a nearby Tatooine vista?? 😉

Lukas: that’s probably a typo. Although either way this once again brings up the recent problem of the naming of planets in multiple systems, one that shall only increase in the foreseeable future…

Ok, thanks! I just used the opportunity to check if I’d got a hang of exoplanet naming.
Is it possible to have planets orbiting a gravitational center point from all of these stars, as if there was only one star? I would imagine so.

Robert E – From the surface of the planet, the sun would appear as a small twinkling star, since it is 22 light years away.

You probably meant how big would the star GJ 667C appear from the surface of the planet. The diameter of GJ 667C is 1/3 of The Sun, but the planet is only 5 million miles away from the star (or about 18.5 times closer than Earth is to Sun), so the apparent diameter of GJ 667C from the planet would be about 6 times what we see of the Sun from Earth.

Since the apparent area of the disk varies by the square of the diameter, the star GJ 667C would appear about 36 times the area of our Sun!!!

Maybe we got lucky that a nearby deficient star has planets, or maybe the earlier work is off a bit and stars like this do have planets. Either way, it again implies planets are extremely abundant in the galaxy.

If memory serves, our Sun is actually somewhat anomalously metal-rich for this area of the Galaxy and relative to its nearest neighbours, right? We also know at least the Methuselah / Genesis pulsar planet (PSR B 1620-26 b) formed in Globular cluster Messier 4 a whopping 13 billion years ago under, presumably, much metal-poorer conditions. Plus I think we’ve found a handful of exoplanets orbiting somewhat metal poor~ish stars – HR 8799 a.k.a. “Gadolabove” being one such as its a Lambda Bootis type star and those are metal poor as well as having a Vega style dust disk and being a Gamma Doradus variable. So I’m not altogether surprised by that.

Still good news with very positive implications.

I do wonder how life and civilisations might be different evolving on a metal poor world though?

@1. Chris
“At that close distance, the planet must be tidally locked. Also don’t red dwarfs typically have large flare activity, so it might be difficult for advanced life to take hold.”

Those two factors would counteract each other somewhat, no? If it’s tidally locked, then half the planet would be largely protected from flares. The night side might be too cold to sustain advanced life, but an atmosphere can do wonders to convect heat.

I don’t get too excited, though. There are enough planets that odds are some harbor life, but many of these observations are based on size of planet and distance from its star. Well, if that was all it took, then Venus should be viable.

I am not convinced that this planet is a rocky world. The low metallicity implies a lack of material to form a rocky planet- so instead of a super-Earth, perhaps it is a mini (or midi?) Neptune. In any event, if there is not a lot of material to form a core, then perhaps this planet, if rocky, has no magnetic field, and thus it may have lost its atmosphere over time. As several posters have pointed out, many Red Dwarfs are flare stars, with active chromospheres.
So- right now, all we have is a lower limit to the mass, a period and a figure for possible temperature. But- would this planet not be a great candidate for some of the imaging missions that have been thought of, such as the TPF? Or even that ‘pinhole camera’ idea from a few years ago?
In any event, this is great news, and we live in an amazing time.

I too have heard the Sun is anomalously metal-rich for its current surroundings (the stars forming in, for instance, Orion, have caught up to whatever cloud the Sun formed in 4.6 billion years ago); this has lead astronomers to consider it forming closer to the galactic core where star formation has been running somewhat faster. The latest stuff I’ve seen suggest that while metallicity IS correlated to presence of planets, it starts picking up at stars somewhat more metal-poor than the Sun, so that’s still ok.
HR 8799 may actually be a 30 Myr old star in the Columba moving group, which I would think implies slightly-higher-than-solar metallicity. It’s possible the metallicity you found was wrong, if it was derived by fitting observations to a model rather than actually trying to measure chemical abundances.

Methuselah, as a pulsar planet, may not have formed the same way these “regular” planets have (how do you survive a supernova at a distance of 23 AU?), so metallicity might not have mattered for whatever process formed that planet.

@10. Doug:
EVERY habitable planet orbiting an M dwarf should be tidally locked. Somewhere around spectral type M0, the outer edge of the habitable zone slips inside the tidal locking radius (see the link in my name). The saving grace is that this planet’s orbital eccentricity is possibly higher than Mercury’s, which would allow it to spin in some kind of resonance (Mercury is 3 days:2 orbits)

The last few years it seems that planets are multiplying like rabbits. We should be concerned at the rate the planets are multiplying we’ll soon be so over-run with them we will have to move our solar system to Andromeda just to avoid the crowd.

In all seriousness- fantastic news. I don’t believe life could only exist on a planet such as ours- seems a little too convenient. However, even if “carbon/water” based life WERE the only form of life- the chances of it existing elsewhere get more and more.

It almost seems proposterous to believe that there is no life outside our solar system. There simply has to be- the odds of life, with so many planets, moons, stars, galaxys makes the idea that we are “special” seem ludicrous.

@Phil, fascinating as always. Question, though. You say that red dwarfs outnumber “stars like the Sun 10 to 1”. What’s your source for that? The HR curve? And is that all G type stars, or yellow stars, or what?

I am curious if the other two stars are close enough to provide any energy to the surface of the planet. Even if it is tidally locked- could A and B provide enough energy for the dark side of the planet to possibly maintain simple “earth-like” life- assuming there is an atmosphere and some weather system to distribute heat a little around the globe.

I’m assuming that the other two stars would only provide minimal light to the planet and would appear as merely large extra-bright stars. Is this correct?

The best source for that is the RECONS group- check my name for the link.

The statistics at that site are for all known systems within 10 pc (32.6 light years) of the Sun, and that’s probably the closest to complete sample we have.
As of January 1, 2012, we know of (published, that is) 20 G stars within 10 pc of the Sun (including the Sun), and 248 M stars. That’s a little over 10 times as many M stars as G stars.

If you consider that there are 50 systems within 5 parsecs (16.1 light years) (look for the RECONS Top 100 closest stars list) there should be 8 times as many stars within 10 pc (2x2x2, it’s a volume thing), or 400 systems. We only know of 259 systems, and because G stars are bright and obvious nearby, the ~141 remaining systems probably all have faint M dwarf primaries. Then there are all the currently undiscovered faint companions… The final number is probably going to be more like 20 M: 1 G.

an interesting thought experiment: if the planet is tidally locked and has a sufficiently convective atmosphere, it is possible that GJ 667Cc could be warm enough to support liquid water. life on the anti-solar side of the planet would be protected from flares, and would presumably depend on light from GJ 667A&B with a 28-day “day.”

As for planets around metal-poor stars, certainly when you consider gas giants there is a strong trend observed, but smaller planets seem to get produced more easily as you go to lower metallicities. GJ 667 C has two strikes against it when it comes to gas giants: low mass and low metallicity, but perhaps this made it easier for the smaller planets to survive (you can really cause a lot of havoc when gas giants start crashing around the neighbourhood).

Regarding HR 8799 it is a Lambda Boötis star – these are chemically-peculiar stars which show odd abundance patterns, it is not a simple case of them being metal poor. In the case of HR 8799 the carbon and oxygen abundances are slightly elevated above solar, but elements heavier than sodium are depleted. Note that A-type main sequence stars are notoriously prone to all kinds of chemical peculiarities. One of the leading hypotheses to explain the Lambda Boötis phenomenon is that the star may have accreted large quantities of material that have polluted their outer layers: the observed abundances at the photosphere may not necessarily reflect the bulk composition of the star as a whole.

@20 Beau Kemp
The planet just orbits the one red dwarf. According to Wikipedia, GJ 667 C orbits the other 2 stars between 56 and 215 AU, meanwhile the planet is ~0.05 AU from it’s star. I’m sure there must be some gravitational perturbations, but should be fairly stable.

Even if the planet is tidally locked , it could still harbor life at its twilight regions. And with 2 other suns moving around in the same solar system there could be a partial sunrise/set. This might give life a chance as “we know it”.

I was just going to say much the same as andy on the planets vs metallicity. As I remember the latest Kepler conference (it’s on the web) as giants seem to have a problem with metallicity but terrestrials not, and M stars seem to more easily produce planets to boot.

Some earlier studies suggested that “metallicity is an overall problem” IIRC which is probably why you still hear this, and in the old days before there was even 500 exoplanets the catalogs trended as “metallicity is only a problem for smaller than average metallicity”.

Apparently YMMV and look out for the curves on the road!

@ Larian LeQuella:

While it is indeed a datapoint, we still suffer from a lack of datapoints. It could just be coincidence that there are two systems within 22 lightyears that have earthlike worlds around them. We need to find a few more before definitively state that implication (not that I actually disagree with you, I just think it may be a bit premature at this point to come to that conclusion).

If you had taken a static sample, this would be correct. But now we sample as we go, so an early detection do in fact predict many planets.

By that measure we were expected to see habitable planets about now. And we did!

Next up, observing inhabited planets. Hopefully the observatories are up to the task to find for example oxygenated atmospheres of close habitables even without JWST…

No, because the planet is much closer in. The Earth’s orbit’s radius is 93 million miles, so its circumference (2*pi*r) is 584 million miles. The Earth covers this distance in 365 days = 8760 hours, so its average speed is 66,700 mph.

This planet orbits at 5 million miles, so its orbital circumference is 31 million miles, which it covers in 28 days, or 672 hours. So it’s average speed is 46,000 mph, which is slower than the Earth’s.

“What about the other two stars? Would they put the planet in a similar situation to the one in Isaac Asimov’s Nightfall, where there’s essentially 24/7 daylight?”

I don’t think that would happen. The two remaining stars are not in the same orbital plane as the red dwarf and the planet own plane. If you check Celestia the two stars are below the said plane, kinda like the southern cross is for the Earth. But even if they were somehow in the same plane, they would be far too distant to actually create the eternal daylight situation. Both of the stars are about 150 AU away form the planet. That’s more than 4 times the distance between Pluto and the Sun. Knowing also that the stars are dimmer than our Sun (each of them only 17% as much), I don’t think they would shine all that much. Also according to Celestia each of the twin stars has an apparent magnitude of -14.7 seen from the planet, which would be roughly 6 times as bright as full moon (-12.7). I think per each unit of magnitude the object gets 2.5 times brighter…

It could just be coincidence that there are two systems within 22 lightyears that have earthlike worlds around them.

Don’t forget Gliese 581d, which is only 20 ly away. That makes 3 planets more earth-like than Mars is within a roughtly 20ly sphere centered on Sol. That’s pretty impressive. (And given our excitement about the potential habitability of Mars, I’d say that any planet more like earth than mars deserves to be categorized as “potentially habitable” and “earth-like” to an arbitrary definition of “like”.)

And if we include Gliese 581c, we have at least 5 planets within the class that includes earth, Venus, and Mars.

and would presumably depend on light from GJ 667A&B with a 28-day “day.”

Pluto is 3.6 billion miles from the sun, and the sun appears as just a very bright star from Pluto’s orbit. GJ667A&B, both being smaller than the sun, would most certainly be just very bright stars in the sky from GJ667C b’s vantage.

I wonder what it would be like to be an astronomer on such a world. Would the presence of two stars so near by be a boon? Or would the additional light obscuring the rest of the sky be a bane?

Dang it – why does FTL travel have to be so damn impossible?! I SO want to see planets like this, go down to their surface, study their history, geography (or would that be exogeography? Xenography?), maybe even their xenobiology, and gaze upon their strange skies, and strange sunsets.

I don’t see here any discussion about the shape of this alleged planet’s orbit, how stable it is or how long it has existed in it’s current orbit. Somewhat useful information if one is going to insist on surreptitiously turning all those “might”s “maybe”s and “if”s into “billions of planets”.

All I see is more gushy euphoria about yet another unconfirmed discovery in yet another article that deftly slips from speculation into certainty that we’ll see “another Earth…soon”. Another Gliese 581g anyone?

Nobody says
Dang it – why does FTL travel have to be so damn impossible?!

I just got done looking at Venus and a very bright Uranus practically combined into a single point of light in the sky (so cool) , and Jupiter and Moon and Sirius, Orion…(I mean winter has it goin’ on in some regards.) I come in and read “why does FTL travel have to be so damn impossible?!” and I began thinking about some funny and probably fruitless oratorical remark instead I became enamored with this thought:

Is there a sort of what you could call reverse speed limit?

To my understanding particle accelerators generate enough concentrated energy to move particles at very near 299 792 458 m / s, but never exceeding this for all intensive purposes “definition of impossible.” I don’t have for practicalities sake any understanding about the great physics; φύσις physis “nature”, and thus my ability to comprehend antimatter-matter collisions without a background in QM or GR is minimal.

However, is there the opposite of speed or velocity in mathematics?

I am just thinking that sometimes things seem so far away but if you just stop for awhile you can sometimes one day behold that which was so impossibly far away (these mostly being human related goals, yes, I am applying something I have learned about patience to the idea of FTL travel, get the bouncer).

I suppose if something could just stop, actually be at rest without experiencing any pulls or pushes or tugs in any directions from the forces of nature, if mass was allowed to rest indefinitely, I am imagining maybe some exploratory physics would entail.

I was trying to explain to my son the other day these tidbits:

speed of Earth in orbit is about 29,790 m/s
speed of the Sun moving through the Milky Way roughly 220,000m/s
speed of Milky Way through the Local Super Group again roughly 600,000 m/s…

so I was telling him it is unfair of me to ever ask him to stop moving entirely or to just be completely still, because really everything is just hurtling over distances and then I explained to him relative to his position on Earth, could he please stop entirely and then he said “but I can’t, things in my body don’t ever stop moving, like my blood and my mind and my skin”

What if we could just stop though? Am I really traveling at these incredible speeds? Everything seems a little tough to contemplate. Perhaps to cross the boundary for FTL travel is to not be affected by any forces whatsoever. Considering the forces of nature I don’t think its possible for anything with mass to ever not have some speed. As there is a theoretical absolute zero at which entropy reaches its minimum value could there also be an absolute zero speed and could this just be a little bit faster than anything with mass can move.

If traveling beyond the speed of light is impossible and that means we can never reach GJ 667Cc in any of our lifetimes, then maybe by just stopping completely we might have a chance.

At any extent maybe I am just imagining some science fiction. The Michael Crichton in me is thinking about explaining away the absolute values. I know you cannot travel a negative speed or distance, buut

Good Day

ps, unlike the AGW blogs, its okay to turn something into a FTL discussion is it not? 😉

Whether or not this revelation will prove to be worth while, or even accurate, remains to be seen.

Some things are sure:

The universe is a big place, almost infinite
The chances of intelligent life existing must be more than 1:infinity-1
Earth is not the only place inhabited by intelligent life.
Humans do not have the sole claim to “intelligence”.

Considering the expansion of the Universe can anything with mass just stop moving entirely? As impossible as it appears to travel beyond the speed of light is it also as impossible to reduce speed to absolute zero? To not be affected by time & space seems local to the idea of actually being able to move FTL.

Stop moving entirely in respect to what? If it stopped moving in regards to it’s star (which would cause it to actually fall into the star but you know what I mean) it would still be moving in regards to the other stars in the system, to us and the rest of the universe. All part of relativity actually. Everything is measured in relation to something else.

I don’t think that would happen. The two remaining stars are not in the same orbital plane as the red dwarf and the planet own plane. If you check Celestia the two stars are below the said plane, kinda like the southern cross is for the Earth.

The orbital plane of the planet is unknown. In Celestia we default to depicting the planet’s orbital plane being parallel to the ecliptic plane (the plane of the Earth’s orbit), except in the case of additional information which allows further constraints on the orientation such as transits.

Not sure if the orbit of GJ 667 C around the AB pair is known either for that matter…

Dang it – why does FTL travel have to be so damn impossible?! I SO want to see planets like this, go down to their surface, study their history, geography (or would that be exogeography? Xenography?), maybe even their xenobiology, and gaze upon their strange skies, and strange sunsets.

Maybe, with sufficient advances in imaging technology, you could, within your lifetime, do some of these things virtually. If sufficiently high resolution imaging of a planet’s surface could be obtained, a virtual environment of it could be reconstructed, and various devices with haptic feedback might even allow a person to experience what it would be like to be there, touching things.

Though I’m guessing such technology won’t be within any of our lifetimes… :(.

But virtualy gazing into the alien skies would be the easiest of all. Even with today’s computer technology, and our knowledge of the surrounding stars, it should be possible to reconstruct what the night sky would look like from the surface of that planet, and produce a computer simulation of it (and since it is only 22 ly from earth, my first guess is that many of the constellations won’t be that different from what we see here on earth….)

Neal deGrasse Tyson mentioned in one of his books that the HZ is more of a misnomer. What a planet really needs is an energy source, not necessary a certain distance from the sun.

A good example of this is Europa, which receives it’s energy from Jupiter’s gravitation. That is why many astronomers think there may be liquid water on a moon that is far, far outside the “HZ”.

He also brings up the point that a planet ejected from an early solar system may have enough energy (at least initially) to develope life in interstellar space. In this case it would be a form of geologic energy.

I think the general public has heard too much about the habitable zone, and believe that life requires a certain distance from the sun, etc, which is not at all true. As was mentioned, Venus IS in the habitable zone, yet it has the hottest atmosphere of all Sol’s planetary bodies.

Complete layperson here- what does a 28 day orbit do to its atmosphere? i.e. does it get blown off at that speed? Compressed in the direction of it’s orbit?

Things get “blown off” when moving at speed because of air pressure. The moving object bumps into static air, and the resultant pressure differential produces a force acting counter to the direction of motion. The magnitude of this force is a function of both the speed of the moving object (relative to the medium it is going through), and the density of the medium.

Out in the vacuum of space, what is the medium the planet would be moving through that provides this resistance, and what is it’s density (I am fairly certain that the luminiferous ether has been debunked….)? We’re basically talking about just a thin smattering of particles from the stellar wind. I think that if gravity is strong enough to hold the atmosphere in, period, then its probably strong enough to hold the atmosphere for pretty much any reasonable speed. (My math skills are sufficiently advanced to calculate this out to relativistic speeds….)

But in a perfect vacuum (which of course does not exist in nature), you ought to be able to go at infinite speed (well, infinitely close to the speed of light, anyways) and experience no loss of atmosphere.

I think the general public has heard too much about the habitable zone, and believe that life requires a certain distance from the sun, etc, which is not at all true. As was mentioned, Venus IS in the habitable zone, yet it has the hottest atmosphere of all Sol’s planetary bodies.

There is the issue, that usually gets glossed over, of time frame to consider as well, here.

Say you have a planet in the habitable zone, too small for a magnetic field, but formed in such a way that it starts out with a thick atmosphere. We say that such a planet is not habitable because it will lose it’s atmosphere to the stellar wind. But how long does it take to lose that atmosphere? That’s going to depend on the details of how thick the atmosphere is to start with and the strength of the parent star’s wind. If it takes, say 1.5 billion years to lose the atmosphere, and the system is only 1.0 billion years old, then this planet is habitable, and may well have primordial life on its surface. (The poor bastards are doomed, of course, but they’re alive NOW.)

In the case of Venus, lots of climate models do suggest that there was a brief period early in Venus’ history when it had very earth-like conditions. Then the runaway greenhouse kicked in and the planet cooked. This period was very brief, but if aliens happened to observe the solar system in that window, Venus would have appeared habitable to them. Now consider the very high likelihood, using similar climate models, the Earth will go the same away approximate 0.5-1.0 billion years from now. The projections have earth getting a surface temperature upwards of 1000K, at least from one source I recall, and that’s even hotter than Venus (thanks to earth’s water vapor being a substantially more powerful greenhouse gas than CO2). So if aliens were to observe our solar system in the future, after that point, earth would not be observed as habitable.

It could well be that a Venus-like state, and a Earth-like state, far from being separate classes of planets, are actually separate stages in the normal life cycle of a large fraction of earth/venus-like worlds. In some cases the earth-like state is very short, and in others it is very long.

So, in point of fact, a Venus-like world, if defined solely by the characters we use to define exoplanets (ie, the ones we can currently observe, being mainly size, mass, distance from star, and maybe density) IS a habitable world. Whether it is habitable NOW depends on what stage of its life cycle we are observing it in, and I’m not at all certain if we can currently predict that all that well (what would have happened to Venus if a large impact had blown off 99% of its atmosphere just before the runaway greenhouse kicked in?). Sure, the poor Venusian-analog life-forms are doomed to fry. But then again, so are we, poor, doomed Earthlings.

Or consider another example that has been discussed in various threads recently, that of a gas giant planet with a Europa-analogue watery moon, in the habitable zone.

We can say that, in the habitable zone, the icy moon would not be stable, and it would lose its volatiles, and end up like Luna.

Eventually.

But what if that gas giant had only migrated into the habitable zone orbit relatively recently? How much time would it take for the water to be lost? What if the planet had a very extensive magnetic field that actually shielded the moon from the stellar wind?

He also brings up the point that a planet ejected from an early solar system may have enough energy (at least initially) to develope life in interstellar space. In this case it would be a form of geologic energy.

IIRC, he also brought up the interesting factoid that an earth-sized ejected planet retains enough internal heat to keep its geological energy sources going for hundreds of billions of years, while a earth-sized habitable planet circling a sun-like star gets swallowed by a red giant within 10.

This would, of course, make the ejected planets MORE habitable, in the long run, than the ones still bound to sun-like stars!

The universe is a big place, almost infinite
The chances of intelligent life existing must be more than 1:infinity-1
Earth is not the only place inhabited by intelligent life.
Humans do not have the sole claim to “intelligence”.

You forgot one: 15 Billion years is a long, long time. In 4 billion of those years our planet has managed to produce exactly one technological civilization that has been detectable to the universe at large for, at most, 100 years. There are, however, at least a dozen more extant species that could be said to be “intelligent” in that they pass a basic self-awareness test (IIRC all of these are cetaceans, primates or corvidae).

I’d hazard to posit that life is probably ubiquitous, higher lifeforms fairly common and “intelligence” to not be particularly rare. But technological civilizations are statistically rare enough that we may well be the only such in the universe during this tiny slice of time in which we are just that.

@9. Messier Tidy Upper – I too have heard the Sun is anomalously metal-rich for its current surroundings (the stars forming in, for instance, Orion, have caught up to whatever cloud the Sun formed in 4.6 billion years ago); this has lead astronomers to consider it forming closer to the galactic core where star formation has been running somewhat faster. The latest stuff I’ve seen suggest that while metallicity IS correlated to presence of planets, it starts picking up at stars somewhat more metal-poor than the Sun, so that’s still ok. HR 8799 may actually be a 30 Myr old star in the Columba moving group, which I would think implies slightly-higher-than-solar metallicity. It’s possible the metallicity you found was wrong, if it was derived by fitting observations to a model rather than actually trying to measure chemical abundances.

Thanks for that informative reply – cheers!

BTW. I didn’t find the metallicity myself – that’s just what I’ve read in a couple of places which is that HR 8799 (or Gadolabove as I prefer to call it) is listed as a Lambda Bootis type star and these are a metal poor stellar class.

@24. SteveG :

To get a different take on how the seasons could work, take a read of Brian Aldis’ Helliconia trilogy.

That recommendation is seconded by me. Great trilogy with some interesting astronomical world setting that. Excellent read too.

@29. Anders :

If this star is deficient in oxygen, would this mean that its planets would be deficient in oxygen as well? Also, the tidal-locking point seems valid. Can anyone comment on these two queries?

Sure. 😉

Stars and planets obviously vary greatly in composition and just because a star is metal poor doesn’t mean oxygen – a relatively abundant element – won’t be common on a planet, far as I’m aware. I’d expect it will almost certainly be more common there (like everywhere) than heavier elements such as iron, platinum and thorium.

Oxygen is highly reactive and combustible so it will likely usually be combind in oxide (rust) and other compound forms unless it is being constantly replenished so finding it would be a strong indication of probable life of some variety.

Once we thought that Mercury (and Venus too?) would be tidally locked – Isaac Asimov among others writing fictional tales based on a tidally locked Mercury with a permanent sun-facing hot side, dark-side and twilight zone. However we discovered mercury is NOT, in fact, tidally locked but has instead a very slow day – one and a half mercurian days to the mercurian year if memory serves. Think that’s likely due to the gravitational influence of Venus and /or its elliptical orbit plus perhaps an early fast rotation rate?

Assuming GJ 667Cc is tidally locked is usual but it may be unusual perhaps having been born with or aquired an excessively rapid spin that has yet to be slowed fully, perhaps spun up by perturbing influences from nearby planets or a large natural satellite. Don’t count on it – GJ 667Cc probably *is* tidally locked – but we cannot yet be 100% certain of this. At least that’s my 2 cents worth on that query FWIW.

@49. Ron Broberg :

I figure the gravity is between 1.3 and 1.7 earth Gs if the density is about 0.7 times that of Earth’s. The lower density is assumed due to the descriptions of the red dwarf as metal poor.

Interesting. Thanks for that.

@14. ctj : “Messier Tidy Upper, remember that to astronomers, a “metal” is anything other than H or He.”

Stellar surveys – painstakingly counting and marking and classifying stars – show that red dwarfs outnumber all the others. Really bright high mass stars – types O, B, A & the giants – tend to be very rare the higher the mass the rarer the star. Yet thegianst and highmass stars tend to dominate our nightskies because they are cosmic lighthouses – visible across vast gulfs of space whereas red dwarfs are such dim candles that not a single one can be seen without optical aid – and yet they are everywhere.

To find the nearest giant star you ned to go allteh way out toPollux at about 30 light years from Earth – the nearest B type star is Regulus at about 80 light years away and the nearest O type star is hundreds of light years distant. Combined O & B stars actually make up less than 1% of the total population of stars. Ninety percent of stars are main- sequence or dwarf stars.

And is that all G type stars, or yellow stars, or what?

Well G type stars are refered to as “yellow” despite really being more white with just a hint of yellow if that. Stellar class wise -based on surface temperatures calculated via spectra -the prism split starlight we have :

O type stars described as blue,
B stars described as blue-white (or just lumped in as blue)
A stars as white
F stars as white
G stars as yellow
K stars as orange
M stars as red

&
L, T, & now Y stars as brown. With the terms giant, dwarf, sub-giant, sub-dwarf generally being added to complete the describtion of the type of star denoting an individual stars sizer, mass and evolutionary state – all interrelated things.

However, stellar colours are more complex that that in visual and photographic ways for instance Vega (Alpha Lyrae) is often described as blue but is a “white” A0 dwarf which we’re seeing facing pole on – the poles of Vega being hotter than its equator. Enif (EpsilonPegasi) is frequently described as a “yellow giant” despite being technically a K type or orange one and many people call most orange giants (eg. Arcturus, Aldebarran, Pollux) – which will often look more yellow than orange – red! 😉

@ ^ Corrections for clarity because editing time always seems to disappear too quickly. (Like most other time really. Sigh.)

F stars as white yellow-white.

Nb. Called Procyonese dwarfs by some to avoid confusing with white dwarfs which are stellar remnants off the main-sequence. Similarly Sirian is used for A-type main-sequence stars.

a trio of yellow dwarf stars (Alpha Centauri A, Sun, Tau Ceti)

&

To find the nearest giant star you need to go all the way out to Pollux (Beta Geminorum) at about 30 light years from Earth – the nearest B type star is Regulus at about 80 light years away and the nearest O type star is hundreds of light years distant.

To be more precise Regulus is 79 light years distant (Source – Kaler’s stars Regulus page) with the nearest O type star, I think, being Zeta Ophiuchi at 460 light years versus Al Niyat (Sigma Scorpii) at 735 light years although I may be mistaken on that.

I understand why the planet would very likely be tidally locked, and think there is a rather small probability that it might not be. But suppose it isn’t yet, due to a high initial spin rate and other possible influences that have been suggested. Wouldn’t the planet be subjected to uncomfortably huge daily, oceanic tides (if it has oceans like the earth does) and tidal stresses on its crust resulting in very high tectonic activity such as frequent, massive earthquakes and volcanoes?

Suppose, on the other hand, that it is actually two earthlike planets orbiting a common center of gravity which is, in turn, orbiting the star. I know this is extremely unlikely, but is there any way of ruling out that possibility, and how would that effect the habitability of those planets? They would almost certainly be tidally locked to each other and thus possibly, (depending on their distance from each other) have a rotational period that would be shorter than their orbital period around the star.

Another intriguing but probably very highly improbable scenario would be of the gravitational influence of the star being strong enough to overwhelm hypothetical dual planets gravitaional influence on each other in such a way that they are still rotationally tidally locked to the star, but not to each other, and they orbit around each other in the same plane as their orbit around the star so that they both experience day and night by periodically eclipsing each other. Is this a possibility?

On second thought, forget that. They would probably both still have a permanent nightside, illuminated, if at all, only by the sunlight reflected from the surface of the other planet (and, of course, by any other astronomical objects visible in their night skies).

There have been suggestions that some carbon rich dust disks could form carbon planets with asphelt tarry surfaces, layers of diamond and silicon carbide and carbon monoxide skies. Read an article in Astronomy magazine ’bout that years ago.

Citations ~wise, I’m not 100 sure if there are any set rules here. So I’ll just say what I personally like to do for that :

When quoting I like to use @[number of comment being responded to]Personsname – sometimes time if the post numbers may be changing due to moderation, then blockquote (indented paragraph ) for the quote.

For the Opening Post by the blog /article writer I’ll usually just blockquote (indent) the quote. For material quoted from earlier comments I’ll use italics but material from off the thread I’ll usually leave plain text. Plus note the source usually in the author, date university standard eg. (Source : OneOfNone comment 73 -GJ 667C exoplanet thread, 2012 Feb. 9th -6.55 am) with links when I’m quoting online material and pages numbers, book titles /authors and sometimes publishers plus year of publication when quoting printed texts. Titles get italicised usually – the convention I’ve grown up with. Being a lousy typer I stuff things up on occassion but I do try to give credit where its due and allow others to know where my information is coming from so theycan check it themselves if so inclined. Thus the more specific the source info the more helpful it will be for that end.

But that’s just me & I’m probably a little OTT & quirky in this regard compared to most here.

Suppose, on the other hand, that it is actually two earthlike planets orbiting a common center of gravity which is, in turn, orbiting the star. I know this is extremely unlikely, but is there any way of ruling out that possibility, and how would that effect the habitability of those planets?

I like that hypothesis! I think its unlikely but I’d love to find it was correct!

They would probably both still have a permanent nightside, illuminated, if at all, only by the sunlight reflected from the surface of the other planet (and, of course, by any other astronomical objects visible in their night skies).

Which – don’t forget – includes two other suns Gliese 667 A & B – which may or may not be easily split and would certainly at least be exceedingly bright stars – think much brighter than Venus probably more like crescent or gibbeous moonlight but perhaps from point sources!

@64. Special One – February 8th, 2012 at 3:05 pm :

Earth is not the only place inhabited by intelligent life.

Well it is that we know of for sure! It probably isn’t in reality though.

Humans do not have the sole claim to “intelligence”.

Yeah, my cat tells me that much! 😉

Depends how you define intelligence but many earthly animals arguably are from chimps and dolphins to Jack-Russell X Fox terriers and elephants.

*****
Incidentally, re-reading the first link properly – and the links at the base of that news release I see that Gliese 667 itself is faintly visible in very dark skies for those with good eyesight – apparent magnitude 5.8 in Scorpius conveniently located between the sting and the Antares trio. (Finder chart linked to my name via the original press release.) So, there’s a chance, we can actually see this star with unaided eyes or binocs ourselves which, well, makes me really happy anyhow.

You forgot one: 15 Billion years is a long, long time. In 4 billion of those years our planet has managed to produce exactly one technological civilization that has been detectable to the universe at large for, at most, 100 years.

Caveat : That we know of! 😉

Although, most probably so, yes.

There are, however, at least a dozen more extant species that could be said to be “intelligent” in that they pass a basic self-awareness test (IIRC all of these are cetaceans, primates or corvidae).

D’oh! That’ll teach me to skim read. I see you made the same point there I did in my response to you above. Oops. (Blushes.)

I’d hazard to posit that life is probably ubiquitous, higher lifeforms fairly common and “intelligence” to not be particularly rare. But technological civilizations are statistically rare enough that we may well be the only such in the universe during this tiny slice of time in which we are just that.

I’d agree with all of that – except the “universe” word. Our cosmos is an awfully big place. What may be happening sentient technological species ~wise in the Andromeda galaxy, Messier 51 (the whirlpool galaxie), in Centaurus A or any of the billions of others galaxies is very much an open question.

But, yeah, I suspect biological life may be common with intelligence much rarer and technological species rarest of all. Hard to draw any firm conclusion from a dataset of one living planet mind you. But going on all of prehistory before we developed history I’d say that’s the most likely reality.

*****

“Cosmology also tells us that there are perhaps 100 billion galaxies in the universe and that each contains roughly 100 billion stars. By a curious co-incidence, 100 billion is also the approximate number of cells in a human brain.”
– Page 237, ‘StarGazer’, Dr Fred Watson, Allen & Unwin, 2004.

I’d agree with all of that – except the “universe” word. Our cosmos is an awfully big place. What may be happening sentient technological species ~wise in the Andromeda galaxy, Messier 51 (the whirlpool galaxie), in Centaurus A or any of the billions of others galaxies is very much an open question.

Consider that if the rate of technological intelligence were 1 per galaxy per 10 000 years, this would result in literally quadrillions of such civilizations in lifespan of the universe, and billions if not trillions of them co-existing at the same time, but, unless one of them makes it to K3 status while another in a nearby galaxy is still extant, none of them will ever know that any of the others existed.

But, yeah, I suspect biological life may be common with intelligence much rarer and technological species rarest of all.

Well, since biological life is required for intelligence, and intelligence required for technology, this is a truism, and you’re probably justified in using a word stronger than “suspect” for all of it except the very first part. (ie Life >> Intelligence > Technology is pretty much a truism)

If there had been a species of troodontid, or gorgonopsid, that achieved technological intelligence of a rudimentary level, of, say, sharpened sticks and flaked rocks, or perhaps even all the way up to stone masonry, with an interval existence of even up to a million years (similar to how long human ancestors had such technology levels), before being snuffed by the great mass extinctions, the fossil record from that far back in time is sparse enough that just by bad luck alone, nothing at all of them could be preserved for us to find today.

I have a feeling that we will be turning our Array onto this system this year in order to measure its diameter and get a direct measurement of its HZ. As far as I remember, and looking through their paper, they are using models and other indirect measurements to get the distance of the HZ to the planet. Not to say that those cannot be right, I think we just prefer direct measurements

Amphiox, I think you are probably right about the possibility that there could have been one or more previous sentient species in the earth’s distant past that were wiped out too long ago for there to be enough unequivocal evidence of them still remaining for us to have any reasonable chance of finding it, though I have no way of knowing how likely that is.

I also think that if there really were a way to beat the speed of light limitation that were not too prohibitively difficult or expensive, there would be a strong likelihood that the first sentient species in any given galaxy that discovers that secret would completely overrun and dominate that galaxy long before a second or subsequent species discovers that same secret. Thus the mere fact that alien sentients are not already here makes me very strongly suspect that either the speed of light limitation is insurmountable by any practical means, or that we are the first or only technologically adept species in our galaxy. Both could be true, of course, but I think it is more likely that only the first of those is true.

“Which – don’t forget – includes two other suns Gliese 667 A & B – which may or may not be easily split and would certainly at least be exceedingly bright stars – think much brighter than Venus probably more like crescent or gibbeous moonlight but perhaps from point sources!”

If one could see all the comets in orbit of Sol, clear out to the nearer stars, one could plot a path to that star using those comets as resource pools. Of course, they would need to be moving in the right direction and plane(and, say within 100 million kms or so) for a hypothetical asteroid colony to match velocity and extract their hydrogen, etc. Or one could send AI robotic systems ahead of our colony to tap into the comet and retrieve resources, which would then be carried to the colony as it passed by,,,

I really think that within a millennium or so after we begin colonizing the rest of this solar system, someone will start that trek,,,even if it takes 10,000 years to get to the next system, that’s insignificant for a colony of several million people, whose colony IS their H.O.M.E.. The only use for planets in this scenario is for resources, not to live on,,,and in a few million years, we’d own the galaxy,,,or at least their Oort clouds,,,

And who says they are metal-poor, if the astronomers are made of lead?

I’m sorry to say you have triggered a new pet bugbear of mine, that I have been noticing increasingly over the last two years (roughly). Lots of people do it, so please don’t feel like I’m having a go at you specifically, but I can remain silent on the issue no longer.

Please please please take note:

The verb to lead (pr “leed”) has the past participle led. Note the absence of the “a” in the past participle.

Lead pronounced “led” is the chemical element Pb.

Lead (Pb) / led is an example of a homophone, where two (or more) words with different meanings have the same pronunciation but different spellings.

English is rife with homophones (I believe there are hundreds of examples). With these words, there are only two clues as to which version of the word you mean to use – the spelling and the context. By neglecting the alteration of spelling, you force your reader to deduce your meaning from context alone. This interrupts the flow of the text and coincidentally causes my inner grammar nazi to explode in outrage.

@Nigel #86, this has been a pet peeve of mine too. It is somewhat suprising to me how many people (some of whom seem otherwise quite articulate and intelligent), who post to various blogs I have visited, repeatedly make this same error. I suppose that one of the things that leads people into this error is the fact that the past participle of “to read” is spelled “read”, though it is pronounced “red.” One can be easily misled into the error of thinking that “to lead” necessarily follows that same pattern if enough years have elapsed since one last reviewed the grammar and spelling that should have been learned in primary school.

Complete layperson here- what does a 28 day orbit do to its atmosphere? i.e. does it get blown off at that speed? Compressed in the direction of it’s orbit?

Since the planet is moving through the vacuum of space, nothing happens to the atmosphere as a result of the panet’s orbital velocity.

However, a planet’s atmosphere will be affected to some extent by the solar wind from the parent star. If the planet has a magnetic field, then its atmosphere will be mostly unaffected by this. If the planet has no magnetic field (or a trivially weak field), then a strong solar wind could eventually strip the lighter elements from the atmosphere. This is an oversimplification, but I hope it gets the basic idea across.

Beam me aboard scotty. I’d believe Japanese Godzilla movies were real before i’d beleive some of the garbage I hear coming out of the mouths of our so called scientists. I think they watch too much television!

Great Story!!!
You mentioned that a cloudy planet can hold heat better by way of the greenhouse effect. That is at best, an over-simplification. Actually, the greenhouse effect is not related to the clouds but instead by the composition of the atmosphere. For example, CO2 and more effectively, CH4 (methane) are powerful greenhouse gases. They also do not form clouds here on Earth. Our clouds are H2O and will reflect a great deal of incoming solar radiation, preventing that radiation from reaching the deep atmosphere or the Earth’s surface, there-by providing a cooling effect.
A simple experiment involving 2 identical soda bottles can be done to prove this. Place a thermometer in each. Cap the first with only air and the second after blowing in CO2 or some other greenhouse gas. Place both in a sunny spot and watch the second bottle get hotter quicker. This depends only on the composition of the gas. Notice there are no clouds in either bottle.
Venus has a permanently clouded sky and a run-away greenhouse effect but it’s atmosphere is very high in the greenhouse gas, CO2. I would submit that it is the greenhouse gas in the atmosphere and not the clouds that keep it so hot there.
It would be impossible to say which direction a planet’s clouds would push the HZ envelop without knowing more about the composition of those clouds (and the rest of the atmosphere).
Still, great article and nicely written. Thanks!!!

Chris (#27) and amphiox… You would only notice a *change* in velocity, not the absolute velocity. I learned this the other day, after reading Brian Greene’s excellent discussion of special (i.e. constant-velocity) Relativity.

So yeah, the only weird stuff you’d notice would be collisions with interstellar stuff with a different relative velocity to yours. Like neutrinos (there’s no charge for them!), solar wind particles, teapots, etc. Except for neutrinos, of course. 😉 Confused? So am I…